1. Field of the Invention
This invention relates to a braking device for a power winch, particularly to one having a braking lining provided independently, able lessen wear and prolong service life of the braking lining, having great beneficial result in use and convenient in replacing of the braking lining.
2. Description of the Prior Art
Generally, a braking device for a power winch must be able to stop the motor timely and carry out braking instantly whether the power winch is motionless and not in use or is slinging up and lowering down heavy loads. However, when a conventional power winch is normally driven by a motor to hoist or lower the steel rope (whether there is heavy loads hung thereon), the braking action will automatically be released for smoothly hoisting and lowering the steel rope. A braking device for a power winch, as disclosed in a U.S. Pat. No. 6,520,486, titled “BRAKING DEVICE FOR MOTIVE WINCH”, which was a patent of the inventor of the present invention, includes a reduction box provided therein with a sectional shaft, an elastic member, a first engraved block, a second engraved block and a clutch base. The first engraved block is fitted on the sectional shaft but unable to drive each other and has its outer circumferential edge secured with a braking lining able to contact with or disengage from the frictional surface preset in the reduction box. The elastic member is assembled on the first engraved block, able to produce proper reverse torsional force relative to the first engraved block; therefore, when the braking lining on the first engraved block is in a motionless state, it will be forced to push against the frictional surface formed in the reduction box, ready to carry out braking. The second engraved block is engaged with the sectional shaft for rotating synchronously. The first and the second engraved block are respectively formed with a different slope able to closely contact with each other for pushing the braking lining on the first engraved block to move and perform or release braking, and also respectively formed actuating projections to be actuated to rotate by the projecting blocks fixed on the inner side of the clutch base. The clutch base is driven to rotate by the motor spindle, which is inserted through the sectional shaft (but unable to drive each other) and has its outer end connected with the clutch base. Thus, when the motor is operated, its motor spindle will actuate the clutch base and the two engraved blocks to rotate together to let the braking lining move away from the frictional surface in the reduction box and release braking so as to enable the steel rope to be hoisted or lowered smoothly. When the motor stops operating, the reaction draw force coming from the heavy loads hung on the steel rope will force the slope of the second engraved block to push the slope of the first engraved block and actuate the first engraved block and the braking lining on its outer circumferential edge to move and closely contact with the frictional surface in the reduction box, thus attaining effect of braking.
By so designing, the braking device for a motive winch in this US patent has the following defects.
1. When the motor is operated, the clutch base will actuate the first and the second engraved block to rotate synchronously, and the braking lining assembled on the first engraved block will always be rotated together with the first engraved block, easy to cause wear to the braking lining.
2. The braking lining is firmly secured on the outer circumferential edge of the first engraved block; therefore, in case the braking lining has to be replaced with a new one, both the braking lining and the first engraved block have to be replaced together, inconvenient in use and not conforming to economic gain.